低频与中高频荷载对结构钢及其焊接节点疲劳寿命的影响研究

钢结构的疲劳试验研究采用低频、中频和高频加载,疲劳寿命是否会有差别,或者怎样的差别？一直是试验者希望找到答案的问题。作者以结构钢及其焊接件为对象,对低频(30Hz以内)与中高频(100Hz左右)加载的疲劳试验数据(包括本文作者和其他学者)进行分析对比,研究低频与中高频加载对疲劳寿命的影响,疲劳试验涉及高强度Q460钢板及其对焊节点、普通强度Q345钢板对焊节点。研究发现低频与中高频加载的疲劳寿命有很大的差别,无论是钢材还是对焊节点,低频加载比中高频加载的疲劳寿命长或疲劳强度高。对这种现象的机理也作了解释。建议对承受低频的疲劳荷载的工程钢结构,其疲劳试验应切合实际地应采用低频疲劳试验机加载。若采用高于低频的疲劳试验机加载,则会显著地低估疲劳寿命。

Effect of Loading with Low and Medium-High Frequencies on Fatigue Life of Structural Steel and Welded Connection

Is there any difference or what difference is in fatigue life between fatigue tests of steel structures under loading with low, medium and high frequencies. It is a problem for experimenters to find answer. Comparative analysis of fatigue test data (including tests carried out by the authors in this paper and other scholars) was carried out for structural steel as well as weldment under loading between low frequency below 30Hz and medium-high frequency around 100Hz. The effects of low and medium-high frequency loading on fatigue life was investigated. The fatigue tests dealt with high strength steel Q460 and its butt-welded joints, as well as butt-welded joints of normal strength steel Q345. It was found from the current research that there was substantial difference in fatigue life between low and medium-high frequency loading. The former had longer fatigue life or higher fatigue strength than the latter, no matter whether it was steel or butt-welded joints. The mechanism for this phenomenon was also explained. It is suggested that for engineering steel structures subjected to low frequency fatigue loading, fatigue tests should be conducted using low frequency fatigue testing machine. It may significantly underestimate fatigue life if a fatigue testing machine with a frequency higher than low frequency is used.